EQ vs. Tube Rolling?

I know it's fun to buy and install new stuff, but is there any reason why you can't just use an equaliser to do what any tube does? Is there any measurement that would favor a tube that gives extra bass vs EQ'ing up the bass?

No.  You can roll different tubes that even the most objective ears says impart different tonal characteristics then measure the FR of the different tubes and they all measure w/ the same curve.  EQ changes the FR curve, Tubes dont.  At least ones that work.  Where the perceived difference lies is the question and some of us are working on it, when we get more time.  Maybe it's even order harmonics, maybe it's something else.

When people say a tube gives extra "micro detail" don't they just mean that it ups the treble a bit? Why not just EQ up the treble? Potentially big $$$ for these rare tubes vs nothing for an EQ. 

No, that's fake detail.  The micro detail I hear in tubes is throughout the frequency range, treble, mids and bass.  Deeper inner resolution that strips a recording.  I have yet to hear a SS device compare to the best tube amps in sheer resolving power.  I'll be looking more into more higher end SS devices to see if I can find something comparable.  Note, not all tube amps are good, uncolored transparent devices.  So don't take someones poor experience w/ SS or tubes as a reference.  So far devices like the O2, V200, DAC1, Beta22 all fall behind in this regard.  IME, YMMV.

It's curious to me that if distortion is causing the euphonic 'natural' experience of a tube amp, that I can extract more resolution from a noisier device.  So something in that argument seems amiss to me.  

Plus the notion that tube amps are a warm, gooey, muddled, inaccurate mess is a bunch of BS.  So are bad SS amps.

(Note that 'warmth' is used in two different ways often.  Bassy/colored vs smooth/analog.  Natural is a tricky word and so is neutral as that's relative to an empirical measure at the source versus perception at the ear.)

@Anaxilus: Thanks for the response. So any decent tube does nothing to change the FR? Very, very interesting.

@Anaxilus: Thanks for the response. So any decent tube does nothing to change the FR? Very, very interesting.

It's certainly fascinating how something that is essentially a horrible lightbulb can be so good at making music. I'll have to do research on tube harmonics and such.

Thanks to all for the replies.

They have no place in the play-back chain and they do NOT sound 'better' than a Solid-state amp .

That is not an 'argument', tubes/valves have more distortion than transistors, PERIOD .

It's the exact reason they are used by musicians and recording engineers .

When recording you are 'designing' sounds and often various forms of coloration are desirable .

As a guitarist I own several tube-amps (EL34,EL84,6L6 and 6V6) and I love them .

Bassists tend to disagree, most of the high-end bass-amp rigs are solid-state jobs .

But I would NEVER use a tube-amp to play back the recorded music .

Good tubes are expensive and rare and belong in instrument-amps .

They have no place in the play-back chain and they do NOT sound 'better' than a Solid-state amp .